There is a well-known magnetic gripper (Soviet patent document 1,082,749) consisting of a U-shaped casing of magnetically sort material in which at least two pairs of permanent magnets with control windings on them are housed. One of the magnets of each pair of magnets is neutralizing. One of the poles of the permanent magnets rests on the upper part of the U-shaped casing, and the other pole in a common pole terminal.
The disadvantages of this well known magnetic gripper are the reduced lifting capacity due to large magnetic losses in the magnetic circuit, the high electric power consumption, the penetration of the magnetic field deep into the sheet material, the small gripping force for thin sheets, and the complicated and energy consuming material demagnetization and the regulation of the force of gripping.